And I'm Rachel Martin in Singapore, where history has unfolded. It began with a handshake. President Donald Trump and Kim Jong Un, the leader of North Korea, then signed what they described as a historic agreement.

(SOUNDBITE OF PRESS CONFERENCE)

PRESIDENT DONALD TRUMP: We're prepared to start a new history. And we're ready to write a new chapter between our nations.

MARTIN: President Trump described the deal as a comprehensive plan to denuclearize North Korea. But the document they signed is not long on details. NPR White House correspondent Scott Horsley joins me now in Singapore, where he has had a front row seat to the remarkable events of the past 24 hours or so.

Hey, Scott.

SCOTT HORSLEY, BYLINE: Good morning, Rachel.

MARTIN: Can you explain what exactly these two leaders signed? What's in this deal?

HORSLEY: Well, it's a short document. It spills over just a little more than a page. And it basically reiterates Kim Jong Un's commitment to move towards denuclearization on the Korean Peninsula, whatever that means. And it includes a security guarantee from President Trump towards the Republic of North Korea. There's not very much detail at all about what the timetable would be or what the verification procedures would be to see that North Korea is in fact dismantling its outlawed nuclear weapons program, which has been the U.S. objective here. There is some reference to North Korea helping to repatriate the remains of U.S. service members who were killed during the Korean War all those decades ago.

But we learned a little bit more that was not actually in the agreement when President Trump gave his news conference this afternoon. One of the things he mentioned is that North Korea has committed to dismantle one of its missile engine test sites, which would be at least one step towards getting rid of the capability to deliver nuclear weapons.

MARTIN: OK.

HORSLEY: And then the president himself also talked about a commitment that he's made to North Korea to suspend joint military exercises with South Korea.

MARTIN: This would be one of the security protections that he alluded to...

HORSLEY: Absolutely.

MARTIN: ...Suspending these joint military exercises, which is a really significant deal.

HORSLEY: It's a major concession, although the president didn't present it that way. But it is definitely a major concession by the United States. Remember that when Kim first broached the idea of holding this summit, one of the sort of offers he put on the table was that he wouldn't complain about those joint military exercises. Ordinarily, North Korea has raised a stink about the U.S. practicing war games with its South Korean partners. They consider that a provocative act. The U.S. has said it's purely a defensive act. But Trump said, yeah, I do think it's provocative, and we're not going to do it.

He apparently didn't communicate this to the South Koreans, who were caught off guard by this announcement. Even though South Korea is generally very supportive of this new attitude between the U.S. and North Korea, they seemed flabbergasted by this remark that the president - they're going to halt the war games. And it's going to be something that Secretary of State Mike Pompeo will probably have to explain when...

MARTIN: Right.

HORSLEY: ...He arrives in Seoul later this week.

MARTIN: What does the U.S. get for that concession?

HORSLEY: Well, that's the question. I mean, what has North Korea - I mean, North Korea has not really committed to do anything additional in this agreement than they had committed to in the past.

MARTIN: They have done so before and reneged.

HORSLEY: Exactly. And they don't even, you know, add any more meat to their commitments in this agreement, so it's a major step from the president. We should say that when he was campaigning, then-candidate Donald Trump often complained about the cost of the U.S. military presence in South Korea. He continues to complain about that as commander in chief. And so he's kind of looking for an opportunity to draw down U.S. troops. He says he's not planning to do that right now, but he'd like to do it at some point. And of course, that would only add to questions others in Asia have about U.S. staying power in the Asia-Pacific region.

MARTIN: What about the optics? I mean, this was so rife with symbolism. And we saw the American flag flying right next to the North Korean flag, a flag that can't even be flown legally in South Korea.

HORSLEY: Many American flags flying next to many North Korean flags. It was a flag-draped, you know, day from morning till afternoon. There was a great deal of pageantry here. It seemed as if the White House put sort of more effort into choreographing the optics than into actually working out the nitty-gritty of the agreement.

I was reminded of an event that President Trump had during the campaign, when he showcased a big pile of what he said were Trump Steaks, Trump-branded steaks...

MARTIN: Right.

HORSLEY: ...Which, on closer inspection, turned out to have been bought from a local butcher shop. Similarly, I think people are going to be asking, the president has sold us a lot of sizzle here with this agreement. We are going to want to see some evidence that there is real beef behind these commitments that North Korea has supposedly made.

Secretary of State Mike Pompeo said the verification is going to be what we have to look for. And that's what people will be watching for in the days and weeks and months to come because we didn't see any evidence of that verification here today.